With the improvement of wireless network infrastructure, mobile application services based on various wireless network schemas develop rapidly. Generally, a mobile station may conduct a simple control over an application service process on a network server by sending a control message.
Usually, there is an one-to-one correspondence between the content of a control message sent by the mobile station and a key on the mobile station (of course, a key can be shared in a case where the contents of the control messages appear in turn, for instance, the play key and the pause key for controlling the media can be shared. When this key is pressed consecutively, the key alternately sends a control message with different content). Therefore, due to the limitation of the size of the generic mobile station, there are not sufficient keys for service control, limiting thereby the service control functions provided by the mobile station to the user.
For instance, in terms of a mobile streaming media service which provides a mobile multimedia broadcast service to the user, since a user terminal is typically provided with four navigation keys only, the user may use those four keys to realize a basic control over the streaming media including forward, backward, pause/play, stop. Assume the mobile streaming media service adopts a Real-time Streaming Protocol (RTSP). An example of a forward operation during playing is described below, which illustrates a process of a terminal providing a service control function to the user.
1. A streaming media service utilizes an RTSP protocol to play a streaming media to a terminal.
2. When playing up to the tenth second, the user presses the forward key. The terminal sends a PLAY message in the RTSP protocol to the streaming media server and inserts, in a RANGE field of the PLAY message, information of a time point where the user wants to skip to. Usually, the intended time point is determined by adding a fixed value set internally by the terminal (assume 15 sec) to the current time (10th sec), which is 25 sec for the value of RANGE in the PLAY message transmitted by the terminal. This indicates that the terminal wants the streaming media server to start playing program at the 25th second.
3. After the streaming media server receives the control message PLAY, the server analyzes parameters of the message and returns a success message to the terminal, indicating that the server accepts this command and broadcasts the program starting from the 25th second.
At the user end, it appears that the user presses a forward key at the 10th second and the user is then presented with the content starting from the 25th second. The user considers that the forwarding function is accomplished.
The backward operation is similar to the above mentioned forward operation, except that the value of RANGE in the PLAY message transmitted from the terminal is obtained by subtracting an internal fixed value from the current time.
Generally, the default values for forward and backward are set by the terminal software and they can not be modified through an interface. Therefore, the user can only forward or backward the streaming media program with a fixed time interval when pressing the forward or backward key of the navigation keys. When the program is long, for instance, 10 minutes, and if the user needs to move forward to a specified time, e.g., the 6th minute, based on the above assumption the user may probably need to press the forward key for 24 times to achieve the effect, which is inconvenient for the user.
In practice, the RTSP protocol also provides richer control functions such as “double rate forward” and “double rate backward”. That is, a dedicated SCALE field can be employed in the PLAY message to carry a parameter indicating the scale of the play speed, e.g., 2, 0.1, −4 may indicate 2× forward rate, 0.1× forward rate, 4× backward rate, etc. However, considering the mechanism of implementation of the existing control function, in order to provide these extended functions, the terminal needs to be provided with additional dedicated keys for the operation of the corresponding n× forward rate and n× backward rate. Accordingly, major modifications to the existing key arrangement and control software of the terminal, etc., are required, which is not conducive to the promotion and application of the services.